71661665 has 4 divisors (see below), whose sum is σ = 85994004. Its totient is φ = 57329328.

The previous prime is 71661661. The next prime is 71661679. The reversal of 71661665 is 56616617.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 56616617 = 311 ⋅182047.

It can be written as a sum of positive squares in 2 ways, for example, as 53479969 + 18181696 = 7313^2 + 4264^2 .

It is a cyclic number.

It is not a de Polignac number, because 71661665 - 2² = 71661661 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (71661661) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7166162 + ... + 7166171.

It is an arithmetic number, because the mean of its divisors is an integer number (21498501).

Almost surely, 2^71661665 is an apocalyptic number.

It is an amenable number.

71661665 is a deficient number, since it is larger than the sum of its proper divisors (14332339).

71661665 is a wasteful number, since it uses less digits than its factorization.

71661665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14332338.

The product of its digits is 45360, while the sum is 38.

The square root of 71661665 is about 8465.3213169968. The cubic root of 71661665 is about 415.3641068319.

The spelling of 71661665 in words is "seventy-one million, six hundred sixty-one thousand, six hundred sixty-five".